Το CMake είναι το πιο διαδεδομένο εργαλείο για να "χτίσεις" projects γραμμένα σε C++ για το 2021. Το CMake δε μεταγλωτίζει το ίδιο τον κώδικα αλλά παράγει τις κατάλληλες παραμέτρους για άλλα εργαλεία (π.χ. make) τα οποία αναλαμβάνουν τη μεταγλώτισση.  Η χρήση εργαλείων όπως το CMake είναι μονόδρομος όταν ένα έργο σε C++ περιλαμβάνει πολλά αρχεία, διάφορες παραμέτρους, εξωτερικά dependencies κλπ. Σε αυτή την περίπτωση η ανάπτυξή του γίνεται εκθετικά δυσκολότερη όσο το μέγεθός του αυξάνεται, εάν δεν υιοθετηθεί χρήση εργαλείων όπως το CMake. 邏 Στο εργαστήριο θα δείξουμε πως μπορούμε να στήσουμε ένα τυπικό project γραμμένο σε C++ και θα καλύψουμε τα πιο βασικά σενάρια που χρειάζεται να γνωρίζει κάποιος όπως: ✅ Παραγωγή εκτελέσιμου αρχείου ✅ Καθορισμός του include path ✅ Δημιουργία βιβλιοθήκης για static ή dynamic linking ✅ Ελεγχος των διάφορων compilation flags ✅ Δημιουργία functions εντός του CMake ✅ Παραμετροποίηση μέσω options

1. Introduction to CMake
Dimitris Platis
dimitris@platis.solutions

2. [grcpp]
👍facebook.com/grcpp
👍meetup.com/grcpp-athens
● Knowledge spreading
● Discussions
● Development culture
● Networking

3. About me Dimitrios Platis
● Grew up in Rodos, Greece
● Software Engineer @ Zenseact,
Gothenburg
● Course responsible @ DIT112 & DAT265
Gothenburg University / Chalmers
● Interests:
○ Embedded systems
○ Software Architecture
○ API Design
○ Open source software & hardware
○ Robots, Portable gadgets, IoT
○ 3D printing
○ Autonomous Driving
● Website: https://platis.solutions

4. How about you?

5. What is CMake?
CMake is a software that manages the
way C/C++ projects are built. It has the
ability to simplify the build process of
projects with large or complex code
layouts and is compiler-agnostic.
It is considered the de facto standard for
building C/C++ projects.

6. When is a build
system
necessary?
● Avoid hard-coding paths
● Build a package on more than one
computer
● Support multiple operating systems and
compilers
● Describe how your program is
structured logically, not flags and
commands
Source: An Introduction to Modern CMake

7. Why do you
need to learn
CMake?
● 55 to 80% of C++ developers use it
● The vast majority professional C++
projects use it
● Cross-platform
● Well-supported by IDEs
● Relatively easy to get started with
● Makefiles and building with the command
line simply do not scale

8. Create binaries

9. Create binary with command line
// src/main.cpp
#include <iostream>
int main()
{
std::cout << "Hello World" << std::endl;
return 0;
}
$ g++ src/main.cpp
$ ./a.out

10. Create binary with CMake
cmake_minimum_required(VERSION 3.12)
project(IntroToCmake)
add_executable(hello_world src/main.cpp)
$ mkdir build
$ cd build
$ cmake ..
$ make
$ ./hello_world

11. Generated build/Makefile
# Default target executed when no arguments are given to make.
default_target: all
# The main all target
all: cmake_check_build_system
$(CMAKE_COMMAND) -E cmake_progress_start /home/me/projects/intro-to-cmake/build/CMakeFiles
/home/me/projects/intro-to-cmake/build//CMakeFiles/progress.marks
$(MAKE) $(MAKESILENT) -f CMakeFiles/Makefile2 all
$(CMAKE_COMMAND) -E cmake_progress_start /home/me/projects/intro-to-cmake/build/CMakeFiles 0
# Build rule for target.
hello_world: cmake_check_build_system
$(MAKE) $(MAKESILENT) -f CMakeFiles/Makefile2 hello_world

12. Let's spice things up
// src/greeter.h
#ifndef GREETER_H
#define GREETER_H
void greetClass();
#endif
// src/greeter.cpp
#include "greeter.h"
#include <iostream>
void greetClass()
{
std::cout << "Hello GRCPP" << std::endl;
}
$ g++ src/main.cpp src/greeter.cpp
$ ./a.out

13. CMake allows for structured & version controlled scaling
add_executable(hello_world src/main.cpp
src/greeter.cpp)
$ make
$ ./hello_world

14. Set include path
#include <foo/Foo.h>

15. mv src/greeter.h include/greeter/greeter.h
We want to start including "greeter.h" as
"greeter/greeter.h"
#include "greeter.h" ➡ #include "greeter/greeter.h"
$ g++ src/main.cpp src/greeter.cpp -I include/

16. mv src/greeter.h include/greeter/greeter.h
target_include_directories(hello_world PUBLIC include) $ make

17. Create libraries

18. libgreeter.a (static library)
add_library(greeter src/greeter.cpp)
target_include_directories(greeter PUBLIC include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC greeter)
$ make greeter
$ ls -l libgreeter.a
> -rw-r--r-- 1 me me 3088 libgreeter.a
$ make hello_world
$ ldd

19. libgreeter.so (dynamic library)
add_library(greeter SHARED src/greeter.cpp)
target_include_directories(greeter PUBLIC include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC greeter)
$ make greeter
$ ls -l libgreeter.so
-rw-r--r-- 1 me me 16856 libgreeter.so
$ make hello_world
$ ldd hello_world
libgreeter.so =>
/home/me/intro-to-cmake/build/libgreeter.so

20. Building libraries with CLI
Static library
$ g++ -c src/greeter.cpp -I include/
$ ar rvs greeter.a greeter.o
$ g++ src/main.cpp greeter.a -I include/
Dynamic library
$ g++ -c src/greeter.cpp -I include/ -fPIC
$ g++ -L . src/main.cpp -l greeter -I include/

21. Set compilation flags
🚩🚩🚩

22. Add universal VS target-specific flags
add_compile_options(
-Wall
-Wextra
-Wpedantic
-Werror
)
$ g++ src/main.cpp -Wall -Wextra -Wpedantic -Werror

23. Disable flag(s) for a specific target
target_compile_options (greeter PRIVATE -Wno-pedantic)

24. Configure the build with options

25. Conditional builds
option(BUILD_ALTERNATIVE_GREETER
"Build the alternative libgreeter" OFF)
if(BUILD_ALTERNATIVE_GREETER)
add_library(greeter SHARED
src/alternative_greeter.cpp)
else()
add_library(greeter SHARED src/greeter.cpp)
endif(BUILD_ALTERNATIVE_GREETER)
target_include_directories(greeter PUBLIC
include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC
greeter)
$ cmake .. -DBUILD_ALTERNATIVE_GREETER=ON

26. CMake functions
⚙

27. Customize your build steps
function(configure_test testExecutable)
# Link against gtest library
target_link_libraries(${testExecutable}
gtest gtest_main gmock_main)
# Disable variadic macro warnings
target_compile_options(${testExecutable}
PRIVATE -Wno-gnu-zero-variadic-macro-arguments)
# Create test name as the capitalized form
string(TOUPPER ${testExecutable} testName)
# Add executable to test suite
add_test(${testName} ${testExecutable}
${GTEST_RUN_FLAGS})
endfunction(configure_test)
add_executable(dummy_test DummyTest.cpp)
configure_test(dummy_test)

28. Takeaways
● We covered only the surface
● Easy things are simple with CMake
● Integration with custom build systems or other
libraries is where the trickery begins
● Start using CMake (or equivalent, e.g. Bazel)
even for personal projects

30. Let's keep in touch!
https://www.linkedin.com/in/platisd/
dimitris@platis.solutions
@PlatisSolutions

31. JetBrains lottery
1 year license for any Jetbrains IDE!
1. Go to: http://plat.is/jetbrains
2. If you won, please stick around until I
contact you
3. If you did not win, better luck next time!
Did you know that as a university student you
can get a free JetBrains license anyway?